Semiconductor laser device

ABSTRACT

A semiconductor laser device has at least one semiconductor laser element, a heat sink having a first bearing area, on which the at least one semiconductor laser element bears, a housing upper part and a housing lower part, which, in the interconnected state, can at least partly surround the semiconductor laser element, and also a sealing for the tight connection of housing upper part and housing lower part. The heat sink services as housing lower part.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a semiconductor laser device with atleast one semiconductor laser element, a heat sink having a firstbearing area on which the at least one semiconductor laser element bearsa housing upper part and a housing lower part, which in theinterconnected state, can at least partly surround the semiconductorlaser element, and sealing means for the tight connection of the housingupper part and the housing lower part. The invention further relates toa semiconductor laser device with at least one semiconductor laserelement and a heat sink on which the at least one semiconductor laserelement can bear.

In order to realize a tightly closing housing in semiconductor laserdevices of the aforementioned type, it is known from the prior art forthe housing lower part to completely enclose the heat sink and thediode, a housing upper part then being placed onto said housing lowerpart. A construction of this type proves to be disadvantageous in termsof firstly the large space requirement of a device of this type andsecondly an additional heat transfer below the heat sink.

Furthermore, heat sinks nowadays generally comprise copper. Copper has adifferent coefficient of thermal expansion than the common semiconductorlaser elements composed of gallium arsenide. For this reason, hardsoldering of the semiconductor laser element embodied as a laser diodebar, for example, on the heat sink is not possible.

BRIEF SUMMARY OF THE INVENTION

The problem on which the present invention is based is to provide asemiconductor laser device of the type mentioned in the introductionwhich requires less space. Furthermore, the present invention is basedon the problem of providing a heat sink for a semiconductor laser deviceof the type mentioned in the introduction which enables hard solderingof the semiconductor laser element on the heat sink.

This is achieved according to the invention by means of a semiconductorlaser device of the type mentioned in the introduction with addedfeatures.

One exemplary embodiment of the invention provides for the heat sink toserve as housing lower part. A configuration of this type obviates aseparate housing lower part surrounding the heat sink. This results in asemiconductor laser device which takes up a smaller space.

In this case, there is the possibility that the heat sink comprises asecond bearing area for the sealing means and/or for a third bearingarea of the housing upper part, said third bearing area interacting withthe sealing means.

In this case, the second bearing area can extend substantially in oneplane.

Furthermore, there is a possibility that the housing upper part and theheat sink serving as housing lower part bear on one another and/or onthe sealing means substantially in one plane.

It may be provided, in particular, that the first bearing area and thesecond bearing area form an angle not equal to 0° and not equal to 180°.By way of example, in this case, the angle between the first and secondbearing areas can be between 3° and 15°, preferably between 5° and 10°,in particular approximately 8°. The angle between the first bearing areaserving for the bearing of the semiconductor laser element and thesecond bearing area serving for the bearing of the upper part has theeffect that the first bearing area is at a greater distance from thesecond bearing area in a direction of the area normal to the firstbearing area at one of its sides than at the side opposite to this oneside. The side at the greater distance will generally be the side atwhich the semiconductor laser element is fitted on the first bearingarea. The angle between the first and second bearing areas thusproduces, particularly ahead of the semiconductor laser element, a stepor cut-out which leaves space for the mounting for example of opticalmeans that the semiconductor laser device comprises. Said optical meanscan serve for influencing the laser radiation emerging from the at leastone semiconductor laser element. Optical means of this type can beformed for example as fast-axis collimation lens.

It may be provided that the sealing means surround the first bearingarea, in particular substantially in the plane of the second bearingarea. By way of example, the sealing means can comprise an O-ring. Inthis case, it may be provided that the sealing means comprise a groovein the second bearing area and/or in the third bearing area forreceiving the O-ring. In particular, in this case, the O-ring cansurround the first bearing area. In this way, it is possible usingsimple means to achieve a good sealing between the housing upper partand the heat sink serving as housing lower part.

It may be provided, for example that the sealing means are configured insuch a way that the tight connection between housing upper part andhousing lower part ensures a leakage rate of less than 2·10⁻⁶ mbar·l·s⁻¹or less than 2·10⁻⁷ N·m·s⁻¹, in particular a leakage rate of less than1·10⁻⁶ mbar·l·s⁻¹ or less than 1·10⁻⁷ N·m·s⁻¹. It is apparent,therefore, that a comparatively low leakage rate can be realized withthe sealing means.

One exemplary embodiment of the invention provides for the heat sink tohave a coefficient of thermal expansion which corresponds to that of theat least one semiconductor laser element, in particular to that ofgallium arsenide. In this way there is the possibility of applying thesemiconductor laser element on the heat sink by means of a hardsoldering.

One exemplary embodiment of the invention provides for the heat sinksubstantially to comprise ceramic, wherein the ceramic has in particularan admixture of carbon nanotubes (CNT). The ceramic can be in particulara ceramic which has a very high conductivity for current and heat inparticular on account of the admixture of the carbon nanotubes. At thesame time, the carbon nanotubes can have the effect that the ceramicalso has a very high breaking strength. In particular, it isadvantageous to set the coefficient of thermal expansion of such aceramic used as heat sink in such a way that it corresponds to that ofthe semiconductor laser element, in particular to that of galliumarsenide.

Such a ceramic could be produced by admixing a suitable amount of carbonnanotubes in the powder used for producing the ceramic.

As an alternative, there is the possibility that the heat sink comprisescopper or copper with CuWo.

Further features and advantages of the present invention will becomeclear on the basis of the following description of preferred exemplaryembodiments with reference to the accompanying figures, in which:

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 shows an exploded illustration of a semiconductor laser deviceaccording to the invention;

FIG. 2 shows a perspective view of the semiconductor laser device inaccordance with FIG. 1;

FIG. 3 shows a perspective view of the heat sink with a semiconductorlaser element of the semiconductor laser device in accordance with FIG.1;

FIG. 4 shows a section in accordance with the arrows IV-IV in FIG. 6;

FIG. 5 shows a section in accordance with the arrows V-V in FIG. 6;

FIG. 6 shows a plan view of the semiconductor laser device in accordancewith FIG. 1;

FIG. 7 shows a plan view of the heat sink with semiconductor laserdevice in accordance with FIG. 3;

FIG. 8 shows a view in accordance with the arrow VIII in FIG. 7;

FIG. 9 shows a view in accordance with the arrow IX in FIG. 7.

DESCRIPTION OF THE INVENTION

It can be seen from FIG. 1 that a semiconductor laser device accordingto the invention comprises a heat sink 1 serving as housing lower partand a housing upper part 2, which can be connected to one another.Furthermore, the semiconductor laser device comprises a housing frontplate 3, which can hold in particular an exit window 4. As analternative, the exit window 4 can be integrated directly into thehousing upper part 2. In addition, the semiconductor laser devicerepresented comprises a semiconductor laser element 5 embodied forexample as a laser diode bar (in this respect see FIG. 7, for example)and also mounting means for a cathode 6 and optical means, which areformed in particular as fast-axis collimation lens 7.

The heat sink 1 has a substantially square base area 8 and a secondbearing area 9 at a distance from the latter. As can be seen from FIG.9, in particular, the second bearing area 9 and the base area 8 form anangle α of approximately 8°, for example, with one another. In the sideview in accordance with FIG. 9, therefore the second bearing area 9slopes down somewhat from left to right, such that the heat sink 1 isformed approximately in wedge-shaped fashion in side view. The heat sink1 therefore substantially represents an obliquely truncatedparallelepiped.

It can be seen from FIG. 4 that not only the heat sink 1 but also thehousing upper part 2 represents an obliquely truncated parallelepiped.The top side is obliquely truncated in the case of the heat sink 1,whereas the underside is obliquely truncated in the case of the housingupper part 2.

The second bearing area 9 does not form the entire surface of the heatsink 1. Rather, a first bearing area 10 is provided in the centralregion of the top side of the heat sink 1, said first bearing areaserving for the bearing of the semiconductor laser element 5. It can beseen from FIG. 3 and FIG. 7, in particular, that the semiconductor laserelement is applied in an end region, namely in the right-hand end regionof the first bearing area 10 in FIG. 7.

As can be seen from FIG. 9, in particular, the first bearing area 10 isparallel to the base area 8 of the heat sink 1. For this reason, thefirst bearing area 10 also forms the abovementioned angle α with thesecond bearing area 9. On account of the angle between the first bearingarea 10 and the second bearing area 9, a significantly larger verticaldistance between the first and the second bearing area 9, 10 arises onthe right-hand side of the first bearing area 9 in FIG. 9 than on theleft-hand side of the first bearing area 10 in FIG. 9. Furthermore, thefirst bearing area 10 does not extend as far as the second bearing area9 on the right-hand side in FIG. 9. Rather, between these two areasthere is a distance that enables a horizontally and vertically extendingmounting space 11. Said mounting space 11 can be seen from FIG. 3, FIG.7 and FIG. 9, for example.

The mounting space 11 can serve for receiving the abovementionedmounting means. The mounting means can comprise a metal plate 12 whichcan be connected to the heat sink 1 by means of screws 13 in the regionof the underside of the mounting space 11 (in this respect, see FIG. 1).A lens holder 14 can be placed onto the metal plate 12, said lens holderholding a fast-axis collimation lenses 7. The lens holder 14 and themetal plate 12 can be connected to one another via a bracket 15 forexample by means of adhesive bonding, soldering or hard soldering.

It can be seen from FIG. 3 and FIG. 7 that a groove 16 for receiving anO-ring (not represented) is provided around the first bearing area 10 inthe second bearing area 9. The O-ring bracket (not represented)therefore surrounds the first bearing area 10 and the mounting space 11without interruption and can bear in sealing fashion on the underside ofthe housing upper part 2, said underside serving as third bearing area.

FIG. 1 furthermore reveals the cathode 6, which can be connected to thefirst bearing area 10 by means of screws 17 and insulating bushes 18. Inthis case, part of the underside of the cathode 6 makes contact with thetop side of the semiconductor laser element 5. In particular, anonconductive layer or a nonconductive material is provided between thatunderside of the cathode 6 which does not bear on the top side of thesemiconductor laser element 5 and the top side of the bearing area 10.

The cathode 6 can be connected to an electrical connection 19 from theoutside through the housing upper part 2. Said electrical connection 19is insulated from the housing upper part 2 by means of an O-ring 20 andan insulating bush 21 (in this respect, see FIG. 1 and FIG. 5).

Furthermore, contact can be made with the top side—serving as ananode—of the first bearing area 10, to which the underside of thesemiconductor laser element 5 is electrically conductively connected, byan electrical connection 22. The latter is for example simply screwedinto a threaded hole 23 in the heat sink 1 (in this respect, see FIG.8).

The housing upper part 2 and the heat sink 1 are connected to oneanother by screws 24; said screws 24 can for example project throughholes 25 and be screwed into corresponding threaded holes 26 in the heatsink 1. Furthermore, both in the housing upper part 2 and in the heatsink 1 serving as housing lower part, continuous holes 27, 28 can beprovided for screws 29, which can for example fixedly screw the entiresemiconductor laser device to an apparatus (in this respect, see FIG. 1,FIG. 4 and FIG. 7 for example).

FIG. 5 and FIG. 8 furthermore reveal a hole 30 in the heat sink 1 whichserves as a receptacle for sensor means.

It can furthermore be seen from FIG. 1 that the housing upper part 2 hasan opening 31 for the passage of the laser radiation 32 emerging fromthe semiconductor laser element 5 (in this respect, also see FIG. 5).The window 4 can be introduced into the opening 31. Furthermore, thehousing front plate 3 also has an opening 33 for passage of the laserradiation 32.

The housing front plate 3 can be connected to the heat sink 1 by screws(not represented). In particular, for this purpose correspondingthreaded holes 34 can be provided on the front side of the heat sink 1and/or of the housing upper part 2. Said screws can project throughcorresponding openings or holes 35 in the front plate 3.

On the left-hand side of the heat sink 1 in FIG. 7, a holding groove 36is provided in the second bearing area 9, which holding groove can servefor the engagement of fixing means. In particular, said holding groove36 serves as a corresponding receptacle for a lug arranged on thehousing upper part 2. The engagement of the lug into the holding groove36 prevents the housing upper part 2 from slipping off in the course ofsecuring it on the heat sink 1 by screwing.

The heat sink 1 can comprise a ceramic material completely or at leastin sections. In particular, it is possible to use a ceramic materialwith which carbon nanotubes have been admixed. Such a ceramic can beproduced by admixing carbon nanotubes in the powder serving as startingmaterial for the production of the ceramic.

Such a ceramic can have a very high thermal and electrical conductivity.Furthermore, it can also have a very high breaking strength on accountof the carbon nanotubes. In particular, it proves to be advantageous ifthe coefficient of thermal expansion of such a heat sink 1 produced fromceramic corresponds to that of the semiconductor laser element 5, and inparticular to that of gallium arsenide. In this way, there is thepossibility of connecting the semiconductor laser element 5 to the heatsink 1 or the first bearing area 10 of the heat sink 1 by hardsoldering.

1. A semiconductor laser device, comprising at least one semiconductorlaser element; a heat sink having a first bearing area including asurface bearing against said at least one semiconductor laser element; ahousing including a housing upper part and said heat sink forming ahousing lower part, said housing upper part and said heat sink, in aninterconnected state thereof, at least partly surrounding saidsemiconductor laser element; and sealing means for tightly connectingsaid housing upper part and said heat sink forming said housing lowerpart; said heat sink formed with a second bearing area including asurface; and wherein an imaginary plane running through said surface ofsaid first bearing area and an imaginary plane running through saidsurface of said second bearing area intersect and form an angle between3° and 15°.
 2. The semiconductor laser device according to claim 1,wherein said heat sink is formed with a third bearing area of saidhousing upper part, said third bearing area interacting with saidsealing means, said second bearing area for said sealing means.
 3. Thesemiconductor laser device according to claim 2, wherein said secondbearing area extends substantially in one plane.
 4. The semiconductorlaser device according to claim 1, wherein said housing upper part issupported on said heat sink serving as said housing lower part.
 5. Thesemiconductor laser device according to claim 1, wherein the angle isbetween 5° and 10°.
 6. The semiconductor laser device according to claim1, wherein the angle is approximately 8°.
 7. The semiconductor laserdevice according to claim 1, wherein said sealing means surround saidfirst bearing area.
 8. The semiconductor laser device according to claim7, wherein said sealing means surround said first bearing areasubstantially in a plane of said second bearing area.
 9. Thesemiconductor laser device according to claim 1, wherein said sealingmeans comprise an O-ring.
 10. The semiconductor laser device accordingto claim 9, wherein said sealing means further comprise a groove formedin at least one of said second bearing area and a third bearing area ofsaid housing upper part for receiving said O-ring.
 11. The semiconductorlaser device according to claim 9, wherein said O-ring surrounds saidfirst bearing area.
 12. The semiconductor laser device according toclaim 1, which further comprises optical means for influencing a laserradiation emerging from said at least one semiconductor laser element.13. The semiconductor laser device according to claim 12, wherein saidoptical means include at least one fast-axis collimation lens.
 14. Thesemiconductor laser device according to claim 12, which comprisesmounting means for mounting said optical means.
 15. The semiconductorlaser device according to claim 12, wherein an interspace is formedbetween said first bearing area and said second bearing area, at leastin a region adjacent said at least one semiconductor laser element, saidinterspace providing a space for mounting said optical means.
 16. Thesemiconductor laser device according to claim 1, wherein said sealingmeans are configured to ensure a tight connection between said housingupper part and said housing lower part to ensure a leakage rate of lessthan 2·10⁻⁶ mbar·l·s⁻¹.
 17. The semiconductor laser device according toclaim 16, wherein said sealing means are configured to ensure a leakagerate of less than 2·10⁻⁷ mbar·l·s⁻¹.
 18. The semiconductor laser deviceaccording to claim 16, wherein said sealing means are configured toensure a leakage rate of less than 1·10⁻⁶ mbar·l·s⁻¹.
 19. Thesemiconductor laser device according to claim 16, wherein said sealingmeans are configured to ensure a leakage rate of less than 1·10⁻⁷N·m·s⁻¹.
 20. A semiconductor laser device, comprising: at least onesemiconductor laser element having a coefficient of thermal expansion; aheat sink having a coefficient of thermal expansion corresponding to thecoefficient of thermal expansion of said at least one semiconductorlaser element; said heat sink having a first bearing area including asurface bearing against said at least one semiconductor laser element;said heat sink having a second bearing area including a surface; andwherein an imaginary plane running through said surface of said firstbearing area and an imaginary plane running through said surface of saidsecond bearing area intersect and form an angle between 3° and 15°. 21.The semiconductor laser device according to claim 20, wherein thecoefficient of thermal expansion of said heat sink corresponds to thecoefficient of thermal expansion of gallium arsenide.
 22. Thesemiconductor laser device according to claim 20, wherein said heat sinkessentially consists of a ceramic.
 23. The semiconductor laser deviceaccording to claim 22, wherein said ceramic includes an admixture ofcarbon nanotubes.
 24. A semiconductor laser device, comprising: at leastone semiconductor laser element; a heat sink bearing consistingessentially of ceramic; said heat sink having a first bearing areaincluding a surface bearing against said at least one semiconductorlaser element; said heat sink having a second bearing area including asurface; and wherein an imaginary plane running through said surface ofsaid first bearing area and an imaginary plane running through saidsurface of said second bearing area intersect and form an angle between3° and 15°.
 25. The semiconductor laser device according to claim 24,wherein said ceramic includes an admixture of carbon nanotubes.